Square Enix, the company responsible for hugely successful franchises such as Final Fantasy and Kingdom Hearts, has licensed use of the Unreal Engine 3 from Epic Games.
Square Enix has a long history of developing large, complex and beautiful titles with their proprietary systems, which are custom developed for a particular console and its available resources. Historically, Square Enix has developed for a single platform and avoided ports of their games. The PC version of Final Fantasy VII and the massively multiplayer Final Fantasy XI are notable exceptions.
According to the press release, Square decided to license the outside engine to "ensure both game quality and development efficiency for next-generation game systems including consoles, PCs and network titles."
The Unreal Engine 3 was chosen because it will help scale their games into multi-core processing modes while freeing up development time for other aspects of game making.